When printing onto photographic paper, it is known that the average red, green, and blue optical density of a large population similar negatives (e.g. film strips with the same DX code) closely represents the average exposure the paper will receive if the optical filters of the monitor system closely match the paper sensitivity. This is described in the paper "The Influence of Film, Paper, and Printer Spectral Characteristics on Photofinishing Performance by W. C. Kress and P. J. Alessi published in Journal of Applied Photographic Engineering Vol. 9, No. 2 April 1983. Because these data are based on many frames from many film strips, this approach provides an accurate predictor for stable films. The average optical density for the particular film type can then be used in conjunction with data from each individual frame to determine the exposure of that frame. This average density data according to film type along with other film data, collectively referred to as "film term data", can be provided by the film manufacture or, alternatively, it can be determined at the printer from cumulative data derived at the film scanner station from films of the same type. In one known type of printer, the film term data is initially inputted using information supplied by the film manufacturer. Subsequently, the printer operator is given the option of updating the film term density data using cumulative film scanner information derived at the particular printer for each film type encountered by the printer.
An alternative to the derivation of average density data from a large population of films is described in commonly assigned U.S. Pat. No. 3,937,573. In this approach, referred to herein as "order scan" algorithm printing, a printer scanner monitor system is used to characterize a particular film strip by using optical data from several frames on the film strip. Once the density data are characterized for that film strip, this data is then combined with data from each individual frame in the strip to determine the exposure of the frame. This approach provides a means of predicting film strip characteristics when there is considerable variability between film strips or where there is no film term information available, e.g. no DX code for the film strip.
It is therefore desirable to combine these two techniques into one system which uses historical data for stable films and current ("order scan") data for films which deviate from the stable historical data or for which there is little historical data available.
Moreover, until now there has been no convenient method by which historical film data derived at the film scanner can be utilized to update automatically the film term data stored in the memory means of the printer to ensure that printer setup conforms to actual experience of the printing lab with films encountered in daily processing. As a consequence, unless the film operator conscientiously initiated an update procedure, for example during power up operation, print exposure conditions would continue to be based on pre-existing film term data and would not reflect the experience gained from processing populations of actual film strips. It is desirable, therefore, to have a method and means for automatically updating existing film term data using historical data generated on an ongoing basis from scanning populations of actual film strips.
Additionally, it is desirable to be able to create automatically a database of film term data for film types encountered by the printer that are not represented in the existing database of film types stored in the printer memory. This is accommodated in the present invention.
Still further, it is desirable to provide for automatic setup of the printer with historically based film term data pertaining to over- and under-slope correction and tungsten correction based on actual experience of the printer with populations of film encountered during processing. This is also accommodated in the present invention.